1. Field of the Invention
The present invention relates to an improvement of an aerosol composition containing insecticidal ingredients.
2. Description of the Related Art
Conventionally, many aqueous insecticides for application or water-based aerosols have been proposed in order to reduce the danger from fire by formulations and decrease the environmental load. However, when the formulations are prepared, aqueous organic solvent, such as alcohols are frequently used in order to attain stable emulsibility because most of the insecticidal ingredients have hydrophobic property. These formulations tend to have inferior insecticidal action on some pests to oil aerosol without water. This results from the difference in penetrability of the insecticidal ingredients from the skin surface of the pests.
The present inventors previously developed a useful aerosol composition containing an aerosol base solution comprising (a) an insecticidal ingredient, (b) a surfactant, (c) an aliphatic hydrocarbon having between 8 and 16 carbons, and (d) water, and (e) a propellant, wherein (c) and (d) are contained in specific amounts, respectively, and filed a patent application (Japanese Patent Laid-open No. 2001-89303). However, most of conventional water-based aerosols for controlling pests are emulsion formulations of water-in-oil type or oil-in-water type. And the above-mentioned useful aerosol composition is also such an emulsion formulation. Consequently, the emulsion formulations are separated into an emulsion phase and a propellant phase in the container containing them. Therefore, it is necessary to shake prior to use to disperse homogeneously the contents.
Water-based aerosols in one-layer type in which the above-mentioned problems were overcome are disclosed in Japanese Patent Publication Nos. Sho 61-45601 and Hei 7-121848. However, dimethyl ether is used as a propellant in these aerosols, and organic solvent, such as lower alcohols is further used in the latter. Therefore, these aerosols do not have sufficient performance for water-based aerosols.
Accordingly, it is an object of the present invention to provide a microemulsion aerosol composition whose hazards of flammability and explosion are reduced and which is one-layer type and therefore does not require to shake a container containing the composition prior to use.
In order to solve the above-mentioned problems, the present-inventors have carried out several researches, and found-out that compositions comprising specific surfactant, specific aliphatic hydrocarbon and water, and a propellant in specific amounts can attain the above-mentioned object, and completed the present invention.
According to a first aspect of the present invention, there is provided a microemulsion aerosol composition containing an aerosol base solution comprising (a) an insecticidal ingredient, (b) a surfactant, (c) an aliphatic hydrocarbon having 8 to 16 carbon atoms, and (d) water, and (e) a liquefied petroleum gas as a propellant, wherein (b), (c) and (d) are contained in amounts of 5 to 20 vol %, 40 to 78 vol % and 15 to 53 vol %, respectively, in the aerosol base solution, and the surfactant (b) is composed of sorbitan fatty esters and polyoxyethylene polyoxypropylene alkyl ethers in a mixing ratio of 1:1 to 5:1.
According to a second aspect of the present invention, in the microemulsion aerosol composition according to the first aspect, the surfactant (b) comprises further polyethylene glycol alkyl ethers.
According to a third aspect of the present invention, in the microemulsion aerosol composition according to the first or second aspect, the propellant (e) is contained in an amount of 40 to 70 vol % on the basis of the volume, of the microemulsion aerosol composition.
The insecticidal ingredient (a) used in the present invention includes, for example pyrethroid insecticidal ingredients, such as phenothrin, permethrin, cyphenothrin, cypermethrin, resmethrin, phthalthrin, allethrin, prallethrin, furamethrin, imiprothrin, etofenprox and the like, silicon-containing insecticidal ingredients, such as silafluofen, organophosphorus insecticides, and the like. Among them, pyrethroid insecticidal ingredients and silafluofen are preferable in the effectiveness and safety. It should be noted that when they have optical or geometrical isomers attributed to asymmetric carbons or double bonds in the chemical structure, the isomers and optional mixtures thereof may be naturally included in the scope, of the insecticidal ingredient in the present invention.
The insecticidal ingredients may be contained in an amount of 0.01-3.0 w/v % on the basis of the total volume of the microemulsion aerosol composition of the present invention. When the amount is less than 0.01 w/v %, desired effect can not be exerted. When the amount is more than 3.0 w/v %, the stability of the microemulsion is deteriorated.
The surfactant (b) in the present invention is characterized by comprising sorbitan fatty esters and polyoxyethylene polyoxypropylene alkyl ethers in a mixing ratio of 1:1 to 5:1.
The sorbitan fatty esters is exemplified by sorbitan monolaurate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, sorbitan monostearate and the like. On the other hand, the polyoxyethylene polyoxypropylene alkyl ethers are exemplified by polyoxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene lauryl ether, polyoxyethylene polyoxypropylene stearyl ether, polyoxyethylene polyoxypropylene decyltetradecyl ether, and the like.
When the mixing ratio between the sorbitan fatty esters and the polyoxyethylene polyoxypropylene alkyl ethers is out of the range of 1:1 to 5:1, microemulsion can not be formed in the aerosol or the stability of the microemulsion is deteriorated even when it is formed, therefore it is not preferable that the mixing ratio is out of the above-mentioned range.
From the viewpoint of the stability of microemulsion, it is preferable to further add polyethylene glycol alkyl esters in the surfactant having the above-mentioned formulation. The polyethylene glycol alkyl esters include for example polyethylene glycol laurate, polyethylene glycol oleate, polyethylene glycol stearate and the like to which the present invention is not limited.
The surfactant may contain other type of surfactants, such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene styrenated phenol, the fatty ester of polyoxyethylene hardening castor oil, diglyceryl alkyl ester and the like, as far as the stability of microemulsion is not deteriorated.
It is suitable to add the surfactant as a whole in an amount of 5 to 20 vol % in the aerosol base solution in the present invention. If the amount is less than 5 vol %, suitable microemulsion can not be formed. On the other hand, if the amount is more than 20 vol %, the surfactant has an adverse effect on the insecticidal effect.
The aliphatic hydrocarbon having 8 to 16 carbon atoms (c) is added in an amount of 40 to 78 vol % in the aerosol base solution in the present invention. If the amount is less than 40 vol %, the insecticidal effect is low because the penetrability of the insecticidal ingredients from the skin surface of the pests is deteriorated. On the other hand, if the amount is more than 78 vol %, hazards of flammability are increased. The aliphatic hydrocarbon includes n-paraffins or isoparaffins, and n-paraffins are preferable in the performance. In addition, other organic solvents may be used as far as the characteristics of the present invention is not deteriorated.
In order to obtain the desired action and effect in the present invention, the mixing amount of water is set to 15 to 53 vol %. If the amount is less than 15 vol %, the problems of flammability is not overcome. On the other hand, the amount is more than 53 vol %, it is difficult to improve the insecticidal effect.
Although a liquefied petroleum gas (LPG) is used as a propellant, dimethyl ether (DME), fluoro carbon gas, compressed gas (nitrogen gas, carbon dioxide gas and the like) and the like may be mixed in a amount that a microemulsion can be formed. It is preferable to use the propellant in an amount of 40 to 70 vol % on the basis of the volume of the microemulsion aerosol composition. If the amount is less than 40 vol %, the sprayed particles become coarse, thereby causing problems in the insecticidal effect. On the other hand, the amount is more than 70 vol %, the safety against flammability is deteriorated. When the amount of the propellant is reduced or compressed gases are used, the ejection pressure is often reduced. As countermeasures therefor, it is useful to use liquefied petroleum gas with an increased ratio of propane/butane.
The present microemulsion aerosol composition may include, for example, acaricides, mildewproofing agents that are active against mold or fungi, etc., anti-fungus agents or bactericides, or synergists for pyrethroid insecticidal compounds, stabilizers, perfumes, bulking agents and the like. The acaricides include, for example, methyl 5-chloro-2-trifluoromethanesulfonamide benzoate, phenyl salicylate, 3-iodo-2-propynylbutyl carbamate and the like. The mildewproofing agents, anti-fungus agents or bactericides include, for example, 2-mercaptobenzothiazol, 2-(4-thiazolyl)benzimidazole, triforine, 3-methyl-4-isopropylphenol, ortho-phenyl phenol and the like.
Generally, the microemulsion aerosol composition of the present invention is placed in a container and used. Because the aerosol base solution in the composition is non-flammability, and the composition is one-layer type due to the mixing of propellant, the container containing the composition need not be shaken when it is used, and the microemulsion aerosol composition exerts excellent insecticidal effect against several pests. Therefore, the present invention provides extremely useful microemulsion aerosol compositions.
The microemulsion aerosol composition of the present invention is generally produced by filling an aerosol base solution into a pressure container to which a bulb portion is attached, and filling a propellant therein under pressure. The aerosol containing the composition of the present invention into a container may have a desired form of bulb, ejection hole, nozzle and the like depending on use, the purpose of use, pests to be controlled and the like. Thus, the present invention can be applied to several embodiments.
The pests to be controlled with the microemulsion aerosol composition of the present invention include, for example, Diptera pests, such as Culex pipiens pallen, Axc3xades aegypti, Chironomidae, Muscidae (house flies), Psychodidase (moth flies), Simuliidae, Tabaninae and the like, Blattidae (cockroaches), Formicidae (ants), Diplopoda (millipedes), centipedes, Isoptera (termites) and the like, and house dust mites, such as Acaridae (acarid mites), Dermatophagoides and the like.
Consequently, the present invention provides a microemulsion aerosol composition whose hazards of flammability and explosion are reduced and which is one-layer type and therefore does not require to shake a container containing the composition prior to use.